Varicella-zoster virus (VZV) open reading frame 4-encoded protein (IE4) possesses transactivating properties for VZV genes as well as for those of heterologous viruses. Since most transcription factors ... [more ▼]

Varicella-zoster virus (VZV) open reading frame 4-encoded protein (IE4) possesses transactivating properties for VZV genes as well as for those of heterologous viruses. Since most transcription factors act as dimers, IE4 dimerization was studied using the mammalian two-hybrid system. Introduction of mutations in the IE4 open reading frame demonstrated that both the central region and the carboxyl-terminal cysteine-rich domain were important for efficient dimerization. Within the carboxyl-terminal domain, substitution of amino acids encompassing residues 443-447 totally abolished dimerization. Gene activation by IE4 was studied by transient transfection with an IE4 expression plasmid and a reporter gene under the control of either the human immunodeficiency virus, type 1, long terminal repeat or the VZV thymidine kinase promoter. Regions of IE4 important for dimerization were also shown to be crucial for transactivation. In addition, the arginine-rich domains Rb and Re of the amino-terminal region were also demonstrated to be important for transactivation, whereas the Ra domain as well as an acidic and bZIP-containing regions were shown to be dispensable for gene transactivation. A nucleocytoplasmic shuttling of IE4 has also been characterized, involving a nuclear localization signal identified within the Rb domain and a nuclear export mechanism partially depending on Crm-1. [less ▲]

Time series of free tropospheric carbon monoxide (CO), ethane (C2H6), and hydrogen cyanide (HCN) column abundances have been derived from observations at the International Scientific Station of the ... [more ▼]

Time series of free tropospheric carbon monoxide (CO), ethane (C2H6), and hydrogen cyanide (HCN) column abundances have been derived from observations at the International Scientific Station of the Jungfraujoch (ISSJ) at 3.58-km altitude in the Swiss Alps (latitude 46.55 degreesN, 7.98 degreesE longitude). The free troposphere was assumed to extend from 3.58 to 11 km altitude, and the related columns were derived for all three molecules from high spectral resolution infrared solar spectra recorded between January 1995 and October 1999. The three molecules show distinct seasonal cycles with maxima during winter for CO and C2H6, and during spring for HCN. These seasonal changes are superimposed on interannual variations. The tropospheric columns of all three molecules were elevated during 1998. Increases were most pronounced for HCN with enhanced values throughout the year, up to a factor of 2 in January 1998 when compared to averages of the other years. The increased tropospheric columns coincide with the period of widespread wildfires during the strong El Nino warm phase of 1997-1998. The emission enhancements above ISSJ are less pronounced, and they peaked after the increases measured above Mauna Loa (19.55 degreesN, 155.6 degreesW). Tropospheric trends for CO, C2H6, and HCN of (2.40 +/- 0.49), (0.47 +/- 0.64), and (7.00 +/- 1.61)% yr(-1)(1 sigma) were derived for January 1995 to October 1999. However, if 1998 measurements are excluded from the fit, CO and HCN trends that are not statistically significant, and a statistically significant decrease in the C2H6 tropospheric column, are inferred. Comparisons of the infrared CO columns with CO in situ surface measurements suggest that the CO free tropospheric vertical Volume mixing ratio profile generally decreases with altitude throughout the year. [less ▲]

A Sun photometer (18 channels between 300 and 1024 nm) has been used for measuring the columnar content of atmospheric water vapor (CWV) by solar transmittance measurements in absorption bands with ... [more ▼]

A Sun photometer (18 channels between 300 and 1024 nm) has been used for measuring the columnar content of atmospheric water vapor (CWV) by solar transmittance measurements in absorption bands with channels centered at 719, 817, and 946 nm. The observable is the band-weighted transmittance function defined by the spectral absorption of water vapor and the spectral features of solar irradiance and system response. The transmittance function is approximated by a three-parameter model. Its parameters are determined from MODTRAN and LBLRTM simulations or empirical approaches using CWV data of a dual-channel microwave radiometer (MWR) or a Fourier transform spectrometer (FTS). Data acquired over a 2-year period during 1996–1998 at two different sites in Switzerland, Bern (560 m above sea level (asl)) and Jungfraujoch (3580 m asl) were compared to MWR, radiosonde (RS), and FTS retrievals. At the low-altitude station with an average CWV amount of 15 mm the LBLRTM approach (based on recently corrected line intensities) leads to negligible biases at 719 and 946 nm if compared to an average of MWR, RS, and GPS retrievals. However, at 817 nm an overestimate of 2.7 to 4.3 mm (18–29%) remains. At the high-altitude station with an average CWV amount of 1.4 mm the LBLRTM approaches overestimate the CWV by 1.0, 1.4, and 0.1 mm (58, 76, and 3%) at 719, 817, and 946 nm, compared to the FTS instrument. At the low-altitude station, CWV estimates, based on empirical approaches, agree with the MWR within 0.4 mm (2.5% of the mean); at the high-altitude site with a factor of 10 less water vapor the agreement of the SPM with the FTS is 0.0 to 0.2 mm (1 to 9% of the mean CWV there). Sensitivity analyses show that for the conditions met at the two stations with CWV ranging from 0.2 to 30 mm, the retrieval errors are smallest if the 946 nm channel is used. [less ▲]

We describe an active application in the field of multicast congestion control for real-time traffic. Our Active Layered Multicast Adaptation Protocol is a layered multicast congestion control scheme ... [more ▼]

We describe an active application in the field of multicast congestion control for real-time traffic. Our Active Layered Multicast Adaptation Protocol is a layered multicast congestion control scheme built on top of an Active Network infrastructure. It benefits from router support in order to obtain information about resources available and to perform the adaptation tasks at the places where shortage of resources occur. It supports heterogeneous receivers through the combination of layered multicast transmission with selective filtering and pruning of layers within the active nodes. Market-based resource management ideas are applied to achieve a resource utilisation level that represents an equilibrium between the user goals and the node operator goals. Our simulation results show that the protocol is feasible and provides adequate reactions to short term and persistent congestion, while keeping the amount of state and processing in the active nodes limited. [less ▲]

The role of nuclear factor (NF)-kappa B in the regulation of apoptosis in normal and cancer cells has been extensively studied in recent years. Constitutive NF-kappa B activity in B lymphocytes as well as ... [more ▼]

The role of nuclear factor (NF)-kappa B in the regulation of apoptosis in normal and cancer cells has been extensively studied in recent years. Constitutive NF-kappa B activity in B lymphocytes as well as in Hodgkin's disease and breast cancer cells protects these cells against apoptosis. It has also been reported that NF-kappa B activation by tumor necrosis factor (TNF)-alpha, chemotherapeutic drugs, or ionizing radiations can protect several cell types against apoptosis, suggesting that NF-kappa B could participate in resistance to cancer treatment. These observations were explained by the regulation of antiapoptotic gene expression by NF-kappa B. However, in our experience, inhibition of NF-kappa B activity in several cancer cell lines has a very variable effect on cell mortality, depending on the cell type, the stimulus, and the level of NF-kappa B inhibition. Moreover, in some experimental systems, NF-kappa B activation is required for the onset of apoptosis. Therefore, it is likely that the NF-kappa B antiapoptotic role in response to chemotherapy is cell type- and signal-dependent and that the level of NF-kappa B inhibition is important. These issues will have to be carefully investigated before considering NF-kappa B as a target for genetic or pharmacological anticancer therapies. [less ▲]

The HST/STIS recorded a detailed time series of images and spectra of the UV emissions from a dawn auroral storm on Jupiter on 21 Sept. 1999. The images show complex and evolving fine structure in the ... [more ▼]

The HST/STIS recorded a detailed time series of images and spectra of the UV emissions from a dawn auroral storm on Jupiter on 21 Sept. 1999. The images show complex and evolving fine structure in the storm, while the emission center remained along the main oval and near dawn in magnetic local time. We serendipitously recorded low resolution UV spectra of the north-south spatial distribution of the auroral emissions. These spectra show far stronger hydrocarbon absorptions than observed in any previous auroral spectra. This indicates an unusually deep penetration of the incident primary particles with respect to the neutral atmosphere, and correspondingly high energy of the primary particles. We can thus use these spectra to identify many complex hydrocarbons in Jupiter's auroral atmosphere which are not normally measured in auroral spectra. These results will be presented along with model fits to the spectra derived both from fitting the observed hydrocarbon absorption features and from comparison with a photochemical model for the expected composition of the auroral atmosphere. This research has been supported by grant GO-8171.01-97A from the Space Telescope Science Institute to the University of Michigan. [less ▲]

The fluorescence spectrum of the C[SUB]3[/SUB] radical in comets is investigated. A theoretical model which takes into account the rotational structure and the different vibrational levels of the bending ... [more ▼]

The fluorescence spectrum of the C[SUB]3[/SUB] radical in comets is investigated. A theoretical model which takes into account the rotational structure and the different vibrational levels of the bending mode Î½ [SUB]2[/SUB] involved in the emision of the 4050 Ã \ group, is elaborated. This model is used to interpret high-resolution spectra of some recent comets. The agreement between observed and theoretical spectra is satisfactory with some realistic assumptions on the electronic oscillator strength and the dipole moment derivative, which determine the relative importance of the rotation-vibration transitions. Different synthetic spectra which show the influence of the Swings effect and the consequences of the change in the heliocentric distance are also calculated and are presented. [less ▲]

The abundance ratios of stable isotopes of the light elements in comets may provide clues of cosmogonical significance. Measuring isotopic ratios in an optical cometary spectrum is, however, a rather ... [more ▼]

The abundance ratios of stable isotopes of the light elements in comets may provide clues of cosmogonical significance. Measuring isotopic ratios in an optical cometary spectrum is, however, a rather difficult task for different reasons. Such measurements require, in particular, very high spectral resolution and are feasible so far only on bright objects. In 1997 we observed comet Hale-Bopp with the 2.6 m Nordic Optical Telescope on La Palma, Canary Islands, with a view to estimating the [SUP]12[/SUP]C/[SUP]13[/SUP]C abundance ratio. About twenty high-resolution (Î» /Î Î» ~ 70000) spectra of the strong CN Violet (0,0) band were secured with the SOFIN spectrograph from 7 to 13 April. The heliocentric and geocentric distances of the comet were then close to 0.9 AU and 1.4 AU, respectively. While the data do show the expected lines of the [SUP]13[/SUP]C[SUP]14[/SUP]N isotopic molecule, we have been surprised to find in addition a number of very weak features, which are real and turn out to be positioned very near to the theoretical wavelengths of lines pertaining to the R branch of [SUP]12[/SUP]C[SUP]15[/SUP]N. After a short description of the reduction and analysis of the data our paper discusses the results derived for [SUP]12[/SUP]C/[SUP]13[/SUP]C and [SUP]14[/SUP]N/[SUP]15[/SUP]N as well as their possible implications. We also present a brief review of the carbon and nitrogen isotopic ratios in various solar system objects and consider the question whether any nucleosynthesis site(s) is (are) known where pairs of values similar to those we measure in comet Hale-Bopp could be produced. [less ▲]

The grafting kinetics of reactive poly(styrene-co-acrylonitrile) (SAN) onto EPR-g-MA was studied under isothermal conditions, at the planar interface of an SAN/ethylene-propylene rubber (EPR) bilayer film ... [more ▼]

The grafting kinetics of reactive poly(styrene-co-acrylonitrile) (SAN) onto EPR-g-MA was studied under isothermal conditions, at the planar interface of an SAN/ethylene-propylene rubber (EPR) bilayer film in relation to the type of reactive groups, NH2 versus carbamate (which is an amine precursor), attached to SAN. The amount of SAN chemically bound to EPR chains at the interface was estimated by selectively washing off the unreacted SAN chains before X-ray photon spectroscopic analysis of the released surface. It is clear that the mutual reactivity of the reactive groups, i.e., the NH2-MA pair versus the carbamate-MA pair, has a decisive effect on the amount of SAN that reacts with EPR-g-MA at the interface. In case of SAN-carb, the grafting reaction is controlled by the thermolysis of the carbamate groups into primary amines. [less ▲]